<div>This study was conducted to evaluate the effects of a conversation-based intervention on the expressive vocabulary and grammatical skills of children with severe motor speech disorders and expressive language delay who use augmentative and alternative communication.</div><div><br></div><div>Eight children aged from 8 to 13 years participated in the study. After a baseline period, a conversation-based intervention was provided for each participant, in which they were supported to learn and use linguistic structures essential for the formation of clauses and the grammaticalization of their utterances, such as pronouns, verbs, and bound morphemes, in the context of personally meaningful and scaffolded conversations with trained clinicians. The conversations were videotaped, transcribed, and analyzed using the Systematic Analysis of Language Transcripts (SALT).</div><div><br></div><div>Results indicate that participants showed improvements in their use of spontaneous clauses, and a greater use of pronouns, verbs, and bound morphemes. These improvements were sustained and generalized to conversations with familiar partners.</div><div><br></div><div><b>Supplemental Material S1.</b> Components of the different study phases. Included are procedures, materials, sample target vocabulary, and sample interactions for baseline, intervention, and generalization phases. </div><div><br></div><div><b>Supplemental Material S2. </b>Tau-U and improvement rate difference (IRD) data for seven of the eight participants. One participant was excluded because there were too few data points available. </div><div><br></div><div>Soto, G., & Clarke, M. T. (2017). Effects of a conversation-based intervention on the linguistic skills of children with motor speech disorders who use augmentative and alternative communication. <i>Journal of Speech, Language, and Hearing Research, 60, </i>1980–1998. https://doi.org/10.1044/2016_JSLHR-L-15-0246</div>